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[ThinLTO] Avoid creating map entries on lookup (NFCI) #164873

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Merged
merged 1 commit into from
Oct 24, 2025
Merged

[ThinLTO] Avoid creating map entries on lookup (NFCI) #164873

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13 changes: 13 additions & 0 deletions llvm/include/llvm/LTO/LTO.h
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Original file line number Diff line number Diff line change
Expand Up @@ -462,6 +462,19 @@ class LTO {
ModuleMapType ModuleMap;
// The bitcode modules to compile, if specified by the LTO Config.
std::optional<ModuleMapType> ModulesToCompile;

void setPrevailingModuleForGUID(GlobalValue::GUID GUID, StringRef Module) {
PrevailingModuleForGUID[GUID] = Module;
}
bool isPrevailingModuleForGUID(GlobalValue::GUID GUID,
StringRef Module) const {
auto It = PrevailingModuleForGUID.find(GUID);
return It != PrevailingModuleForGUID.end() && It->second == Module;
}

private:
// Make this private so all accesses must go through above accessor methods
// to avoid inadvertently creating new entries on lookups.
DenseMap<GlobalValue::GUID, StringRef> PrevailingModuleForGUID;
} ThinLTO;

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12 changes: 6 additions & 6 deletions llvm/lib/LTO/LTO.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1086,15 +1086,15 @@ LTO::addThinLTO(BitcodeModule BM, ArrayRef<InputFile::Symbol> Syms,
GlobalValue::getGlobalIdentifier(Sym.getIRName(),
GlobalValue::ExternalLinkage, ""));
if (R.Prevailing)
ThinLTO.PrevailingModuleForGUID[GUID] = BM.getModuleIdentifier();
ThinLTO.setPrevailingModuleForGUID(GUID, BM.getModuleIdentifier());
}
}

if (Error Err =
BM.readSummary(ThinLTO.CombinedIndex, BM.getModuleIdentifier(),
[&](GlobalValue::GUID GUID) {
return ThinLTO.PrevailingModuleForGUID[GUID] ==
BM.getModuleIdentifier();
return ThinLTO.isPrevailingModuleForGUID(
GUID, BM.getModuleIdentifier());
}))
return Err;
LLVM_DEBUG(dbgs() << "Module " << BM.getModuleIdentifier() << "\n");
Expand All @@ -1108,8 +1108,8 @@ LTO::addThinLTO(BitcodeModule BM, ArrayRef<InputFile::Symbol> Syms,
GlobalValue::getGlobalIdentifier(Sym.getIRName(),
GlobalValue::ExternalLinkage, ""));
if (R.Prevailing) {
assert(ThinLTO.PrevailingModuleForGUID[GUID] ==
BM.getModuleIdentifier());
assert(
ThinLTO.isPrevailingModuleForGUID(GUID, BM.getModuleIdentifier()));

// For linker redefined symbols (via --wrap or --defsym) we want to
// switch the linkage to `weak` to prevent IPOs from happening.
Expand Down Expand Up @@ -1988,7 +1988,7 @@ Error LTO::runThinLTO(AddStreamFn AddStream, FileCache Cache,
LocalWPDTargetsMap);

auto isPrevailing = [&](GlobalValue::GUID GUID, const GlobalValueSummary *S) {
return ThinLTO.PrevailingModuleForGUID[GUID] == S->modulePath();
return ThinLTO.isPrevailingModuleForGUID(GUID, S->modulePath());
};
if (EnableMemProfContextDisambiguation) {
MemProfContextDisambiguation ContextDisambiguation;
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